Nonadiabatic superconductivity in a Li-intercalated hexagonal boron nitride bilayer

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• Li-intercalated hexagonal boron nitride (Li-hBN) is a material with potential superconducting properties.
• Electron-phonon interactions play a critical role in mediating superconductivity.
• The Migdal-Eliashberg formalism is a standard approach for calculating superconducting properties.

Purpose of the Study:

• To investigate the impact of vertex corrections on the electron-phonon interaction in Li-hBN.
• To accurately determine the superconducting critical temperature (Tc) of Li-hBN.
• To assess the technological feasibility of Li-hBN based on its superconducting properties.

Main Methods:

• Calculations performed using the Migdal-Eliashberg (ME) formalism.
• Inclusion of lowest-order vertex corrections (LOVC) in the Eliashberg theory.
• Analysis of the electron-phonon coupling constant (λ), Debye frequency (ωD), and Fermi energy (εF).

Main Results:

• The ratio λωD/εF ≈ 0.46 indicates that vertex corrections are essential for Li-hBN.
• Nonadiabatic effects due to vertex corrections significantly lower the critical temperature (Tc) compared to calculations without them.
• Calculated Tc values with LOVC range from 11.8 K to 19.1 K, while ME calculations predict higher values (21 K to 31.9 K).
• Higher-order vertex corrections (λ^3) further reduce Tc by a few percent.

Conclusions:

• Vertex corrections are indispensable for accurate predictions of superconductivity in Li-hBN.
• The reduced critical temperature due to these effects limits the practical applications of Li-hBN.
• Further research may explore modifications to enhance the superconducting properties of Li-hBN.